Quantitative spectral analysis of the sdB star HD 188112: a helium-core white dwarf progenitor
<i>Context. <i/>HD 188112 is a bright (<i>V<i/> = 10.2 mag) hot subdwarf B (sdB) star with a mass too low to ignite core helium burning and is therefore considered a pre-extremely low-mass (ELM) white dwarf (WD). ELM WDs (<i>M<i/> ≲ 0.3 <i>M<i/><sub...
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| Main Authors: | , , , , , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
05 January 2016
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| In: |
Astronomy and astrophysics
Year: 2016, Volume: 585, Pages: 1-17 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201527445 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/201527445 Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2016/01/aa27445-15/aa27445-15.html 
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| Author Notes: | M. Latour, U. Heber, A. Irrgang, V. Schaffenroth, S. Geier, W. Hillebrandt, F. K. Röpke, S. Taubenberger, M. Kromer, M. Fink |
| Summary: | <i>Context. <i/>HD 188112 is a bright (<i>V<i/> = 10.2 mag) hot subdwarf B (sdB) star with a mass too low to ignite core helium burning and is therefore considered a pre-extremely low-mass (ELM) white dwarf (WD). ELM WDs (<i>M<i/> ≲ 0.3 <i>M<i/><sub>⊙<sub/>) are He-core objects produced by the evolution of compact binary systems.<i>Aims. <i/>We present in this paper a detailed abundance analysis of HD 188112 based on high-resolution <i>Hubble <i/>Space Telescope (HST) near- and far-ultraviolet spectroscopy. We also constrain the mass of the star’s companion. <i>Methods. <i/>We use hybrid non-LTE model atmospheres to fit the observed spectral lines, and to derive the abundances of more than a dozen elements and the rotational broadening of metallic lines. <i>Results. <i/>We confirm the previous binary system parameters by combining radial velocities measured in our UV spectra with the previously published values. The system has a period of 0.60658584 days and a WD companion with <i>M<i/> ≥ 0.70 <i>M<i/><sub>⊙<sub/>. By assuming a tidally locked rotation combined with the projected rotational velocity (<i>v<i/> sin <i>i<i/> = 7.9 ± 0.3 km s<sup>-1<sup/>), we constrain the companion mass to be between 0.9 and 1.3 <i>M<i/><sub>⊙<sub/>. We further discuss the future evolution of the system as a potential progenitor of an underluminous type Ia supernova. We measure abundances for Mg, Al, Si, P, S, Ca, Ti, Cr, Mn, Fe, Ni, and Zn, and for the trans-iron elements Ga, Sn, and Pb. In addition, we derive upper limits for the C, N, O elements and find HD 188112 to be strongly depleted in carbon. We find evidence of non-LTE effects on the line strength of some ionic species such as Si ii and Ni ii. The metallic abundances indicate that the star is metal-poor, with an abundance pattern most likely produced by diffusion effects. |
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| Item Description: | Gesehen am 16.06.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/201527445 |